When the H5N1 bird flu virus made its first appearance at a U.S. poultry farm in February 2022, roughly 29,000 turkeys at an Indiana facility were sacrificed in an attempt to avert a larger outbreak.

It didn’t work. Three years later, highly pathogenic avian influenza has spread to all 50 states. The number of commercial birds that have died or been killed exceeds 166 million and the price of eggs is at an all-time high.

Poultry producers, infectious disease experts and government officials now concede that H5N1 is likely here to stay. That recognition is prompting some of them to question whether the long-standing practice of culling every single bird on an infected farm is sustainable over the long-term.

Instead, they are discussing such strategies as targeted depopulation, vaccinations, and even the relocation of wetlands and bodies of water to lure virus-carrying wild birds away from poultry farms.

But each of these alternatives entails a variety of logistical, economic and environmental costs that may eclipse the intended savings.

“People talk about common-sense solutions to bird flu,” said Dr. Maurice Pitesky, a veterinarian and commercial poultry expert at UC Davis. “But that’s what mass culling is. There’s a reason we’ve been doing it: It’s common sense.”

The current version of the bird flu — known as H5N1 2.3.4.4b — is both highly contagious and highly lethal. It has has plowed through the nation’s commercial chickens, turkeys and ducks with a mortality rate of nearly 100%.

“There’s a reason why they call it ‘highly pathogenic avian influenza,’” said Angela Rasmussen, a virologist at the University of Saskatchewan’s Vaccine and Infectious Disease Research Organization. “It just goes straight through a flock like a hot knife through butter.”

And it’s why most researchers and veterinarians promote mass culling, describing it as humane and cost-effective.

Sparing birds that don’t look sick is a gamble. They may be infected and able to spread the virus through their poop before they have any outward signs of illness. The only way to know for sure is to test each bird individually — an expensive and time-consuming prospect. And if even a single infected bird is missed, it can spread the virus to an entire flock of replacements, Rasmussen said.

It also has the potential to increase the total amount of virus on farms, which is dangerous for human poultry workers, said Dr. Ashish Jha, dean of the Brown University School of Public Health.

The U.S. exports more than 6.7 billion pounds of chicken meat each year, second only to Brazil, according to the National Chicken Council. So as long as foreign buyers are resistant to vaccination, the shots probably won’t be deployed even if egg-laying hens are getting wiped out by the virus.